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Scientists close in on dark matter

Scientists have refined their search for dark matter with the completion of a sophisticated experiment.

An international team of researchers, including from Edinburgh, has completed a series of tests for dark matter – which is thought to account for more than four-fifths of the Universe – using an underground detector in the US.

Although the experiment did not yield any direct evidence of dark matter, the results have enabled scientists to refine their models for dark matter particles.

It will also inform the next generation of experiments that plan to further the search for the material.

Long-term testing

The Large Underground Xenon (LUX) dark matter experiment, at the Sanford Underground Research Facility in the Black Hills of South Dakota, has been operating a series of experiments over the past three years.

The experiment was designed to look for so-called weakly interacting massive particles, or WIMPs, which scientists believe are the most likely fit for a dark matter particle.

Their interaction with ordinary matter is expected to be very faint and difficult to detect.

Sensitive detector

LUX consists of a large tank of cooled liquid xenon surrounded by powerful sensors.

These are designed to detect the tiny flash of light and electrical charge emitted if a WIMP collides with a xenon atom in the tank.

Radiation that might interfere with a dark matter signal, such as cosmic rays, are kept out by the detector’s location a mile underground.

The detector’s extreme sensitivity ensures that if dark matter particles had interacted with the xenon target, the detector would almost certainly have seen it.

Hard-to-reach

Dark matter is thought to account for more than four-fifths of the mass in the universe.

Scientists are confident of its existence because its effects can be seen in the behaviour of galaxies and in the way light bends as it travels through the universe. However, experiments have yet to find a dark matter particle.

The latest results are from the detector’s final 20-month run, which is one of the largest experiments of its type.

Analysis of nearly a half-million gigabytes of data from the detector made use of advanced computer facilities.

Next steps

Future experiments will include the LUX-ZEPLIN (LZ) experiment, which will replace LUX at the Sanford Underground Research Facility.

LZ will have a larger liquid xenon capacity than LUX, to help fend off external radiation.

The LUX scientific collaboration, which is supported by the DOE and National Science Foundation (NSF), includes 20 research universities and national laboratories in the US, UK and Portugal.

These latest findings about what dark matter is, and what it isn’t, are the best yet, and will help improve the next generation of experiments to detect this elusive substance.

Professor Alex MurphySchool of Physics and Astronomy

 

http://luxdarkmatter.org